This invention concerns filiform elements, termed fibers, which may be used for the reinforcement of moldable materials with binder of the hydraulic or non-hydraulic type.
The term "fiber" as used in the present specification is understood to mean a filiform element having a length of 30 to 60 mm, a diameter of 0.5-1.0 mm.
Concerning the reinforcement of moldable materials with hydraulic binder, the technique of reinforcing concrete by steel fibers, filiform elements of short length in metal for example, is currently in common use; the properties of the concrete reinforced by these fibers are thus well known and several types of fibers of various origins to be used for specific applications are currently available. In view of their very small dimensions as compared with reinforced rods, the behaviour of the fiber anchorage in the matrix cannot be predicted starting from the anchorage of reinforcing rods.
The various type of fibers are characterized by their reinforcing effect on the composite material, the effect being caused by their geometrical and mechanical characteristics.
The behaviour of a composite material, i.e. a matrix reinforced with fibers is dependent on the effect of the fiber reinforcement in the matrix close to a crack which appears subsequent to the brittleness of the matrix, as the crack had been caused by breaking stress being exceeded due to dimensional variations (thermal, hygrometric) or to bending or tensile stresses.
Ideally, the fiber reinforcement provides an increase in the breaking energy of the composite material compared to the brittle material-matrix.
The increase in the energy required for failure corresponds to the energy required for the elongation and the breaking of the fiber reinforcement.
This explanation of the intervention of the fiber reinforcement clearly shows the necessity to obtain a single body consisting of ductile fibers and brittle matrix.